Reducing soot and methane emissions may not make as big of an impact as previously thought
Carbon dioxide is a heavy hitter when it comes to global climate change. But there are some other big players that contribute to rising temperatures as well including soot and methane. While some scientists have argued to cut these emissions, a new study suggests that targeting these emissions may make much less of an impact than previously thought.
Methane, when assessed over the course of a century, warms the planet about 25 times as much as the same mass of carbon dioxide does. During the same time frame, soot boosts warming more than 1000 times as much as the same mass of CO2 does. With this evidence, it appears that these two pollutants contribute just as much as CO2. However, methane and soot don’t stick around for as long as CO2 does (methane lingers around for 12 years and soot usually a couple of weeks).
At least two studies published since 2010—one report from the United Nations Environment Programme in 2011 and a follow-up published in Science last year—suggested that significantly reducing the emissions of soot and methane could trim human-caused warming by at least 0.5°C (0.9° F) by 2050, compared with an increase of about 1°C if those emissions continued unabated. But a new analysis suggests that those studies may be overly optimistic.
The authors of the new study, Steven Smith and Andrew Mizrahi, both climate analysts at the Joint Global Change Research Institute in College Park, Maryland, argue that earlier work assumes that dramatic cuts in methane and soot emissions are feasible based on shifting technologies and changes in human behavior. In addition, previous studies estimate that Earth’s climate will rapidly respond to the changes. For example, Smith and Mizrahi say it’s unlikely that by 2035, all home wood-burning stoves will be replaced by clean-burning versions of natural gas or electric power. They’re also dubious that landfills and leaky pipelines will be equipped to capture methane before it escapes into the atmosphere.
In the team’s new analysis, the researchers use what they consider to be more reasonable projections for emissions reductions, a more conservative timeline for the development and deployment of methane-capture technology, and more realistic estimates for how quickly Earth’s climate will respond to reductions in methane and soot. Considering all these factors, Smith and Mizrahi suggest that targeting methane and soot will cause global average temperatures to be only 0.16°C lower by 2050 than they would have been otherwise.
The report can be read in this week's Proceedings of the National Academy of Sciences.
See more at Science/AAAS.
Car exhaust image via Shutterstock.